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    SubjectRe: [linux-usb-devel] usb still sucks battery in -rc7-mm1
    On Sun, 24 Sep 2006, Pavel Machek wrote:

    > I made some quick experiments, and usb still eats 4W of battery
    > power. (With whole machine eating 9W, that's kind of a big deal)...
    >
    > This particular machine has usb bluetooth, but it can be disabled by
    > firmware, and appears unplugged. (I did that). It also has fingerprint
    > scanner, that can't be disabled, but that does not have driver (only
    > driven by useland, and was unused in this experiment).
    >
    > Any ideas?

    (I have not followed the thread, so bear with me if I say anything
    irrelavant)

    I have encountered at least 3 hubs (2 usb2 & 1 usb1) that will consume a
    lot of power (about 2-2.5W if the laptop power consumption readings are to
    be trusted) and heat up a lot (to the point of being too hot to touch for
    more than a few seconds) even when no devices are connected, at least on
    Linux. I have not tested them on a Windows machine to see if this is the
    case there. The USB2 ones used Cypress chips. I do not know what your h/w
    config is, but perhaps this is a similar case ?


    Regards,

    Theodoros Kalamatianos


    PS: Note that the 2-2.5W consumption is the maximum that the laptop USB
    port can provide, and I have noticed that with the hub's external power
    supply connected it heats up even more.
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